The present invention relates to a rolling bearing that is incorporated into various types of machinery to support rotating members such as rotating shafts.
A rolling bearing 1 such as shown in, e.g., FIG. 5 has heretofore been used extensively to support rotating members including rotating shafts. This rolling bearing 1 includes: an outer race 3 having an outer raceway 2 on the inner circumferential surface; an inner race 5 having an inner raceway 4 on the outer circumferential surface; a cage having a plurality of pockets 6, 6 in the circumferential direction; and a plurality of rolling elements 8, 8 which are retained so as to be rollable within the respective pockets 6, 6 and whose rolling surfaces are abutted against the outer raceway 2 and the inner raceway 4. In the conventional rolling bearing the outer diameters of the rolling elements 8, 8 are equal to one another.
To rotatably support, e.g., a rotating shaft within a housing using such rolling bearing 1, the outer race 3 is fitted into and secured to the housing from inside, and the inner race 5 is fitted into and secured to the rotating shaft from outside. When the rotating shaft is caused to rotate under this condition, the inner race 5 rotates inside the outer race 2 based on the rolling of the rolling elements 8, 8 to allow the rotating shaft to rotate within the fixed housing. On the other hand, there is a case where the inner race 5 is fitted into and secured to the outer circumferential surface of the fixed shaft from outside and the outer race 3 is fitted into the inner circumferential surface of a rotor or the like from inside so that the rotor or the like is rotatably supported about the fixed shaft.
The rolling bearing 1 shown in FIG. 5 is a ball bearing using balls as the rolling elements 8, 8. Conventionally, there have also been used rolling bearings using rollers (including tapered rollers and needles) as the rolling elements. While the cage 7 assembled in the rolling bearing 1 of FIG. 5 is a so-called corrugated cage formed by overlapping two elements one upon another, each element being formed by corrugating an annular metal plate, a machined cage 7a such as shown in FIG. 6, which is made of synthetic resin or metal, a crown-shaped cage made of synthetic resin, or a squirrel-cage type retainer (for roller bearings) made of metal or synthetic resin have conventionally been used as cages capable of rollingly retaining the rolling elements 8.
However, the thus constructed and operated conventional rolling bearings 1 address the following problems to be solved. In the conventional rolling bearings 1 the outer diameters of the rolling elements 8, 8 are equal to one another as described above. If the outer diameters of the respective rolling elements 8, 8 are exactly equal to one another, the positional relationship between the respective rolling elements 8, 8 and the pockets 6, 6a of the cages 7, 7a is such as shown in FIG. 6. That is, the distance between the rolling element 8 and the pocket 6a is equal for all the rolling elements 8, 8, which thus imposes no problem. However, it is impossible to make the outer diameters of all the rolling elements 8, 8 exactly the same because of fabrication error that is unavoidable (in other words, size variation per unit container is inevitably present). For example, when JIS class G10 balls whose outer diameter is approximately 2 mm are to be fabricated, variations in outer diameter can be limited to a size variation per unit container of 0.5 .mu.m or less and a diameter variation of 0.25 .mu.m or less, which allowances still brings about some differences.
If the outer diameters of the rolling elements 8, 8 assembled in the rolling bearing 1 vary from one another as described above, the speeds of revolution of the respective rolling elements 8, 8, i.e., the speeds at which the respective rolling elements 8, 8 rotate in the inner race 5 vary due to the size variation per unit container and differences in outer diameter caused by the diameter variation. As a result, the positional relationship between the rolling elements 8, 8 and the pockets 6a, 6a becomes unequal, thereby causing the rolling surfaces of the rolling elements 8, 8 to collide against the inner surfaces of the pockets 6a, 6a irregularly in some cases.
Such irregular collision causes the cages 7, 7a to vibrate depending on how such collision is caused, and produces so-called cage noise. This noise is undesired in that noiseless operation of rotating parts is impaired and unwanted vibrations are produced.